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• How to convert a 32bpp image to an indexed format?

  - by Ed Swangren

  So here are the details (I am using C# BTW): I receive a 32bpp image (JPEG compressed) from a server. At some point, I would like to use the Palette property of a bitmap to color over-saturated pixels (brightness 240) red. To do so, I need to get the image into an indexed format. I have tried converting the image to a GIF, but I get quality loss. I have tried creating a new bitmap in an index format by these methods: // causes a "Parameter not valid" error Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Indexed) // no error, but the resulting image is black due to information loss I assume Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Format8bppIndexed) I am at a loss now. The data in this image is changed constantly by the user, so I don't want to manually set pixels that have a brightness 240 if I can avoid it. If I can set the palette once when the image is created, my work is done. If I am going about this the wrong way to begin with please let me know. EDIT: Thanks guys, here is some more detail on what I am attempting to accomplish. We are scanning a tissue slide at high resolution (pathology application). I write the interface to the actual scanner. We use a line-scan camera. To test the line rate of the camera, the user scans a very small portion and looks at the image. The image is displayed next to a track bar. When the user moves the track bar (adjusting line rate), I change the overall intensity of the image in an attempt to model what it would look like at the new line rate. I do this using an ImageAttributes and ColorMatrix object currently. When the user adjusts the track bar, I adjust the matrix. This does not give me per pixel information, but the performance is very nice. I could use LockBits and some unsafe code here, but I would rather not rewrite it if possible. When the new image is created, I would like for all pixels with a brightness value of 240 to be colored red. I was thinking that defining a palette for the bitmap up front would be a clean way of doing this.

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• What is the Fastest Way to Check for a Keyword in a List of Keywords in Delphi?

  - by lkessler

  I have a small list of keywords. What I'd really like to do is akin to: case MyKeyword of 'CHIL': (code for CHIL); 'HUSB': (code for HUSB); 'WIFE': (code for WIFE); 'SEX': (code for SEX); else (code for everything else); end; Unfortunately the CASE statement can't be used like that for strings. I could use the straight IF THEN ELSE IF construct, e.g.: if MyKeyword = 'CHIL' then (code for CHIL) else if MyKeyword = 'HUSB' then (code for HUSB) else if MyKeyword = 'WIFE' then (code for WIFE) else if MyKeyword = 'SEX' then (code for SEX) else (code for everything else); but I've heard this is relatively inefficient. What I had been doing instead is: P := pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX '); case P of 1: (code for CHIL); 6: (code for HUSB); 11: (code for WIFE); 17: (code for SEX); else (code for everything else); end; This, of course is not the best programming style, but it works fine for me and up to now didn't make a difference. So what is the best way to rewrite this in Delphi so that it is both simple, understandable but also fast? (For reference, I am using Delphi 2009 with Unicode strings.) Followup: Toby recommended I simply use the If Then Else construct. Looking back at my examples that used a CASE statement, I can see how that is a viable answer. Unfortunately, my inclusion of the CASE inadvertently hid my real question. I actually don't care which keyword it is. That is just a bonus if the particular method can identify it like the POS method can. What I need is to know whether or not the keyword is in the set of keywords. So really I want to know if there is anything better than: if pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX ') > 0 then The If Then Else equivalent does not seem better in this case being: if (MyKeyword = 'CHIL') or (MyKeyword = 'HUSB') or (MyKeyword = 'WIFE') or (MyKeyword = 'SEX') then In Barry's comment to Kornel's question, he mentions the TDictionary Generic. I've not yet picked up on the new Generic collections and it looks like I should delve into them. My question here would be whether they are built for efficiency and how would using TDictionary compare in looks and in speed to the above two lines? In later profiling, I have found that the concatenation of strings as in: (' ' + MyKeyword + ' ') is VERY expensive time-wise and should be avoided whenever possible. Almost any other solution is better than doing this.

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• Visual Studio soft-crashing when encountering XAML Errors in initialize.

  - by Aren

  I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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• Recursive N-way merge/diff algorithm for directory trees?

  - by BobMcGee

  What algorithms or Java libraries are available to do N-way, recursive diff/merge of directories? I need to be able to generate a list of folder trees that have many identical files, and have subdirectories with many similar files. I want to be able to use 2-way merge operations to quickly remove as much redundancy as possible. Goals: Find pairs of directories that have many similar files between them. Generate short list of directory pairs that can be synchronized with 2-way merge to eliminate duplicates Should operate recursively (there may be nested duplicates of higher-level directories) Run time and storage should be O(n log n) in numbers of directories and files Should be able to use an embedded DB or page to disk for processing more files than fit in memory (100,000+). Optional: generate an ancestry and change-set between folders Optional: sort the merge operations by how many duplicates they can elliminate I know how to use hashes to find duplicate files in roughly O(n) space, but I'm at a loss for how to go from this to finding partially overlapping sets between folders and their children. EDIT: some clarification The tricky part is the difference between "exact same" contents (otherwise hashing file hashes would work) and "similar" (which will not). Basically, I want to feed this algorithm at a set of directories and have it return a set of 2-way merge operations I can perform in order to reduce duplicates as much as possible with as few conflicts possible. It's effectively constructing an ancestry tree showing which folders are derived from each other. The end goal is to let me incorporate a bunch of different folders into one common tree. For example, I may have a folder holding programming projects, and then copy some of its contents to another computer to work on it. Then I might back up and intermediate version to flash drive. Except I may have 8 or 10 different versions, with slightly different organizational structures or folder names. I need to be able to merge them one step at a time, so I can chose how to incorporate changes at each step of the way. This is actually more or less what I intend to do with my utility (bring together a bunch of scattered backups from different points in time). I figure if I can do it right I may as well release it as a small open source util. I think the same tricks might be useful for comparing XML trees though.

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• Exception in thread "main" java.lang.StackOverflowError

  - by Ray.R.Chua

  I have a piece of code and I could not figure out why it is giving me Exception in thread "main" java.lang.StackOverflowError. This is the question: Given a positive integer n, prints out the sum of the lengths of the Syracuse sequence starting in the range of 1 to n inclusive. So, for example, the call: lengths(3) will return the the combined length of the sequences: 1 2 1 3 10 5 16 8 4 2 1 which is the value: 11. lengths must throw an IllegalArgumentException if its input value is less than one. My Code: import java.util.HashMap; public class Test { HashMap<Integer,Integer> syraSumHashTable = new HashMap<Integer,Integer>(); public Test(){ } public int lengths(int n)throws IllegalArgumentException{ int sum =0; if(n < 1){ throw new IllegalArgumentException("Error!! Invalid Input!"); } else{ for(int i =1; i<=n;i++){ if(syraSumHashTable.get(i)==null) { syraSumHashTable.put(i, printSyra(i,1)); sum += (Integer)syraSumHashTable.get(i); } else{ sum += (Integer)syraSumHashTable.get(i); } } return sum; } } private int printSyra(int num, int count){ int n = num; if(n == 1){ return count; } else{ if(n%2==0){ return printSyra(n/2, ++count); } else{ return printSyra((n*3)+1, ++count) ; } } } } Driver code: public static void main(String[] args) { // TODO Auto-generated method stub Test s1 = new Test(); System.out.println(s1.lengths(90090249)); //System.out.println(s1.lengths(5)); } . I know the problem lies with the recursion. The error does not occur if the input is a small value, example: 5. But when the number is huge, like 90090249, I got the Exception in thread "main" java.lang.StackOverflowError. Thanks all for your help. :) I almost forgot the error msg: Exception in thread "main" java.lang.StackOverflowError at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:65) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:65) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60)

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• HowTo stick QDialog to Screen Borders like Skype do?

  - by mosg

  Hello. A long time ago I tried to find method how to stick QDialog window to screen borders for my small projects like Skype windows do it, but I failed. May be I was looking this code not in the right place, so now I'm looking the solution here, on stack! :) So, does any one have a deal with some kind of such code, links, samples? In my opinion, we have to reimplement QDialog moveEvent function, like below, but that code does not working: void CDialog::moveEvent(QMoveEvent * event) { QRect wndRect; int leftTaskbar = 0, rightTaskbar = 0, topTaskbar = 0, bottomTaskbar = 0; // int top = 0, left = 0, right = 0, bottom = 0; wndRect = this->frameGeometry(); // Screen resolution int screenWidth = QApplication::desktop()->width(); int screenHeight = QApplication::desktop()->height(); int wndWidth = wndRect.right() - wndRect.left(); int wndHeight = wndRect.bottom() - wndRect.top(); int posX = event->pos().x(); int posY = event->pos().y(); // Snap to screen border // Left border if (posX >= -m_nXOffset + leftTaskbar && posX <= leftTaskbar + m_nXOffset) { //left = leftTaskbar; this->move(leftTaskbar, posY); return; } // Top border if (posY >= -m_nYOffset && posY <= topTaskbar + m_nYOffset) { //top = topTaskbar; this->move(posX, topTaskbar); return; } // Right border if (posX + wndWidth <= screenWidth - rightTaskbar + m_nXOffset && posX + wndWidth >= screenWidth - rightTaskbar - m_nXOffset) { //right = screenWidth - rightTaskbar - wndWidth; this->move(screenWidth - rightTaskbar - wndWidth, posY); return; } // Bottom border if (posY + wndHeight <= screenHeight - bottomTaskbar + m_nYOffset && posY + wndHeight >= screenHeight - bottomTaskbar - m_nYOffset) { //bottom = screenHeight - bottomTaskbar - wndHeight; this->move(posX, screenHeight - bottomTaskbar - wndHeight); return; } QDialog::moveEvent(event); } Thanks.

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• working on lists in python

  - by owca

  I'm trying to make a small modification to django lfs project, that will allow me to deactivate products with no stocks. Unfortunatelly I'm just beginning to learn python, so I have big trouble with its syntax. That's what I'm trying to do. I'm using method 'has_variants' which returns true if product has any. Then I'm building a list from variants for this product. Next for every product in this list (I've called it 'set') I check it's stock and set bool variable 'inactive' to true if product has no stocks and to false if there are any. Finally if 'inactive' is false I'm setting self.active to 0. Code fails in line with: set[] = s How to correct it ? def deactivate(self): """If there are no stocks, deactivate the product. Used in last step of checkout. """ if self.has_variants(): for s in self.variants.filter(active=True): set[] = s for var in set: if var.get_stock_amount() == 0: inactive = True else: inactive = False else: if self.get_stock_amount() == 0: inactive = True if inactive: self.active = False return 0 error log : Traceback (most recent call last): File "manage.py", line 11, in <module> execute_manager(settings) File "/home/purplecow/rails/purpledev/site-packages/django/core/management/__i nit__.py", line 362, in execute_manager utility.execute() File "/home/purplecow/rails/purpledev/site-packages/django/core/management/__i nit__.py", line 303, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/home/purplecow/rails/purpledev/site-packages/django/core/management/bas e.py", line 195, in run_from_argv self.execute(*args, **options.__dict__) File "/home/purplecow/rails/purpledev/site-packages/django/core/management/bas e.py", line 213, in execute translation.activate('en-us') File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/_ _init__.py", line 73, in activate return real_activate(language) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/_ _init__.py", line 43, in delayed_loader return g['real_%s' % caller](*args, **kwargs) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/t rans_real.py", line 205, in activate _active[currentThread()] = translation(language) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/t rans_real.py", line 194, in translation default_translation = _fetch(settings.LANGUAGE_CODE) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/t rans_real.py", line 180, in _fetch app = import_module(appname) File "/home/purplecow/rails/purpledev/site-packages/django/utils/importlib.py" , line 35, in import_module __import__(name) File "/home/purplecow/rails/purpledev/lfs/caching/__init__.py", line 1, in <mo dule> from listeners import * File "/home/purplecow/rails/purpledev/lfs/caching/listeners.py", line 10, in < module> from lfs.cart.models import Cart File "/home/purplecow/rails/purpledev/lfs/cart/models.py", line 8, in <module> from lfs.catalog.models import Product File "/home/purplecow/rails/purpledev/lfs/catalog/__init__.py", line 1, in <mo dule> from listeners import * File "/home/purplecow/rails/purpledev/lfs/catalog/listeners.py", line 5, in <m odule> from lfs.catalog.models import PropertyGroup File "/home/purplecow/rails/purpledev/lfs/catalog/models.py", line 589 set[] = s ^ SyntaxError: invalid syntax

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• Undesired "flashing" in Jquery dropdown menu?

  - by Tom

  Hi, I've got the following piece of Jquery: $("#collapse-menu > li > a").click(function() { $(this).toggleClass("expanded").toggleClass("collapsed").find("+ ul").slideToggle("medium"); }); What it basically does is expands or collapses a menu of nested "lists" which contain dropdowns (simplified example): <ul id="collapse-menu"> <li><a class="expanded">Basic Details</a> <ul> <li> <select> .... </select> </li> <li> <select> .... </select> </li> The code works absolutely fine EXCEPT when a large value is selected in any of the dropdowns. At that point, when clicked, the menu will still expand/collapse correctly but "flash" quickly while doing so, as if the entire element was being reset somehow. The data itself is fine but it's the flashing that's unwanted. The strange thing is that if a small value is selected in a dropdown, there's no flashing. When a large value is selected (say, above 30 in an age dropdown of 18-99), the flashing starts happening. Can anyone tell me why this is happening? Or whether there's something not right about the Jquery that's causing this. Thanks. UPDATE: Adding a bounty to this. Have tried a few similar plugins/solutions out there on the net but they all seem to suffer from this "flashing" problem when large dropdown values are selected by default. If it helps, here's a typical similar solution: http://www.i-marco.nl/weblog/jquery-accordion-menu/index_collapsed.html# ... but it suffers from the same problem when dropdowns are added inside the accordion. I hope someone has a clean solution, instead of needing to hack this somehow.

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• Linking buttion to jQuery through service

  - by Ruddy

  I have a small problem that should be very easy to overcome. For some reason I cant work this out. So the problem is I cannot get a button to link to some jquery. My set-up is as follows (showing the relevant code): Default.aspx jQuery: function getContent() { var data = { numberID: 1 }; $.jsonAspNet("ContentService.asmx", "GetContent", data, function (result) { $('#content').html(result); }); } jQuery(document).ready(function () { getContent(); } HTML: <div id="content"></div> ContentService.vb Public Function GetContent(number As Integer) As String Dim sb = New StringBuilder sb.AppendLine("<table>") sb.AppendLine("<tr>") sb.AppendLine("<td class='ui-widget-header ui-corner-all'>Number</td>") sb.AppendLine("</tr>") sb.AppendLine("<tr>") sb.AppendLine("<td>" & number & "</td>") sb.AppendLine("<td><a href='#' id='test' class='fg-button ui-state-default ui-corner-all'><img src='" & Context.Request.ApplicationPath & "/images/spacer.gif' class='ui-icon ui-icon-pencil' /></a></td>") sb.AppendLine("</tr>") sb.AppendLine("</table>") Return sb.ToString End Function So that's the basics of what I have everything works but I'm not sure how to get the button (id='test') to get linked to some jQuery. I want it to be pressed and bring up a popup. I have tried to put the jQuery on default.aspx but this doesn't seem to work unless the button is place in the HTML on that page. $('#test').unbind('click').click(function () { alert('Working'); }); I'm sure this is easy to be able to do but I have been trying for a while and cannot seem to get it to work.

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• Write Scheme data structures so they can be eval-d back in, or alternative

  - by Jesse Millikan

  I'm writing an application (A juggling pattern animator) in PLT Scheme that accepts Scheme expressions as values for some fields. I'm attempting to write a small text editor that will let me "explode" expressions into expressions that can still be eval'd but contain the data as literals for manual tweaking. For example, (4hss->sexp "747") is a function call that generates a legitimate pattern. If I eval and print that, it becomes (((7 3) - - -) (- - (4 2) -) (- (7 2) - -) (- - - (7 1)) ((4 0) - - -) (- - (7 0) -) (- (7 2) - -) (- - - (4 3)) ((7 3) - - -) (- - (7 0) -) (- (4 1) - -) (- - - (7 1))) which can be "read" as a string, but will not "eval" the same as the function. For this statement, of course, what I need would be as simple as (quote (((7 3... but other examples are non-trivial. This one, for example, contains structs which print as vectors: pair-of-jugglers ; --> (#(struct:hand #(struct:position -0.35 2.0 1.0) #(struct:position -0.6 2.05 1.1) 1.832595714594046) #(struct:hand #(struct:position 0.35 2.0 1.0) #(struct:position 0.6 2.0500000000000003 1.1) 1.308996938995747) #(struct:hand #(struct:position 0.35 -2.0 1.0) #(struct:position 0.6 -2.05 1.1) -1.3089969389957472) #(struct:hand #(struct:position -0.35 -2.0 1.0) #(struct:position -0.6 -2.05 1.1) -1.8325957145940461)) I've thought of at least three possible solutions, none of which I like very much. Solution A is to write a recursive eval-able output function myself for a reasonably large subset of the values that I might be using. There (probably...) won't be any circular references by the nature of the data structures used, so that wouldn't be such a long job. The output would end up looking like `(((3 0) (... ; ex 1 `(,(make-hand (make-position ... ; ex 2 Or even worse if I could't figure out how to do it properly with quasiquoting. Solution B would be to write out everything as (read (open-input-string "(big-long-s-expression)")) which, technically, solves the problem I'm bringing up but is... ugly. Solution C might be a different approach of giving up eval and using only read for parsing input, or an uglier approach where the s-expression is used as directly data if eval fails, but those both seem unpleasant compared to using scheme values directly. Undiscovered Solution D would be a PLT Scheme option, function or library I haven't located that would match Solution A. Help me out before I start having bad recursion dreams again.

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• C++ type-checking at compile-time

  - by Masterofpsi

  Hi, all. I'm pretty new to C++, and I'm writing a small library (mostly for my own projects) in C++. In the process of designing a type hierarchy, I've run into the problem of defining the assignment operator. I've taken the basic approach that was eventually reached in this article, which is that for every class MyClass in a hierarchy derived from a class Base you define two assignment operators like so: class MyClass: public Base { public: MyClass& operator =(MyClass const& rhs); virtual MyClass& operator =(Base const& rhs); }; // automatically gets defined, so we make it call the virtual function below MyClass& MyClass::operator =(MyClass const& rhs); { return (*this = static_cast<Base const&>(rhs)); } MyClass& MyClass::operator =(Base const& rhs); { assert(typeid(rhs) == typeid(*this)); // assigning to different types is a logical error MyClass const& casted_rhs = dynamic_cast<MyClass const&>(rhs); try { // allocate new variables Base::operator =(rhs); } catch(...) { // delete the allocated variables throw; } // assign to member variables } The part I'm concerned with is the assertion for type equality. Since I'm writing a library, where assertions will presumably be compiled out of the final result, this has led me to go with a scheme that looks more like this: class MyClass: public Base { public: operator =(MyClass const& rhs); // etc virtual inline MyClass& operator =(Base const& rhs) { assert(typeid(rhs) == typeid(*this)); return this->set(static_cast<Base const&>(rhs)); } private: MyClass& set(Base const& rhs); // same basic thing }; But I've been wondering if I could check the types at compile-time. I looked into Boost.TypeTraits, and I came close by doing BOOST_MPL_ASSERT((boost::is_same<BOOST_TYPEOF(*this), BOOST_TYPEOF(rhs)>));, but since rhs is declared as a reference to the parent class and not the derived class, it choked. Now that I think about it, my reasoning seems silly -- I was hoping that since the function was inline, it would be able to check the actual parameters themselves, but of course the preprocessor always gets run before the compiler. But I was wondering if anyone knew of any other way I could enforce this kind of check at compile-time.

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• Buy or Build for web deployment?

  - by Cannonade

  I have been evaluating the wide range of installation and web deployment solutions available for Windows applications. I will just clarify here (without too much detail, these tools have been covered in other questions) my understanding of the options: NSIS - Free tool that generates setup executables. Small binary. Specialized, sometimes obtuse, scripting language. Inno Setup - Free tools for setup executables. Various binary compression schemes. Pascal scripting engine. WIX - Free toolset to generate MSI binaries. XML definitions language. WIX ClickThrough - Additional tools for packaging, web download and auto update detection (now part of WIX core). InstallShield - Commercial development environment for installation packaging. Generates MSI binaries. C-like InstallScript language. Wise - Commercial development environment for installation packaging. Generates MSI binaries. ClickOnce - Visual Studio supported framework for publishing applications to a webserver, with automatic detection of updates. No support for custom installation requirements (INI files, registry etc ...). Packages setup as an MSI binary. Install Aware - Commercial development environment for installation. Generates MSI binaries. Automatic Update framwork (Web Update). If I have missed any, please let me know. And found some useful discussions of these technologies on StackOverflow: Best Simple Install System Best choice for Windows installers Alternatives to ClickOnce I have worked with a few of these solutions, as well as a handful of proprietary internal installation solutions. They are mostly concerned with packing installations and providing a framework for developers to access the run time environment. With the growing requirement for web deployment and automatic software updates, I expected to find more of a consensus among developers on a framework for web delivery of software and subsequent updates, I haven't really found that consensus. There are certainly solutions available (ClickOnce, ClickThrough, InstallShield Update Service), but they each have considerable limitations (please correct me if I mis-represent any of these). I would be interested in a framework that provided some of the following: Third party hosting/management of updates. Access to client environment (INI files, registry, etc..). User registration/activation. Feedback/Error reporting This is leaving me with the strong impression that the best way to approach the web deployment problem is through a custom built proprietary solution (possibly leveraging existing installer packaging). I have seen this sort of solution work well for a number of successful applications: FileZilla - HTTP request to update.filezilla-project.org to check for updates, downloads an NSIS binary (I think) and then shuts down to run the install.

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• Zend_Form MultiCheckbox not checking boxes

  - by azz0r

  $groups = Model_UserGroup::load_links($object->id); foreach ($groups as $item) { $object->group[$item->group_id] = $item->enabled; } $array_object = (array) $object;//turn the object to an array so zend_form can use it $form->populate($array_object); enabled = 1 or 0 In the form class: $group = new Zend_Form_Element_MultiCheckbox('group'); $groups = Model_Group::load_all(); $new_item = array(); foreach ($groups as $item) { $group->addMultiOption($item->id, $item->name); } However the top group is the only one ever checked. Anyone spot anything glaringly wrong? I know its difficult to get a grasp of my layout/setup for this. Here is the array_object: Array ( [table_name] => User [id] => 112 [updated] => 1269428783 [created] => 1153237813 [group] => Array ( [1] => 1 [3] => 1 ) ) Here is the html zend_form is creating: <dd id="group-element"> <label for="group-1"><input name="group[]" id="group-1" value="1" checked="checked" type="checkbox">Administrator Access</label><br> <label for="group-2"><input name="group[]" id="group-2" value="2" type="checkbox">Content Admin</label><br> <label for="group-3"><input name="group[]" id="group-3" value="3" type="checkbox">Administrator</label><br> <label for="group-4"><input name="group[]" id="group-4" value="4" type="checkbox">Studio</label> </dd> edit: just done a small test and made the $groups (in the first set of code tags) empty and it still ticks the first box. hm Fixed this by doing: // $selected_groups = Model_UserGroup::load_links($object->id); $group_ticks = array(); foreach ($selected_groups as $item) { if ($item->enabled == 1) { $group_ticks[] = $item->group_id;//$form->group->setValue($item->group_id); } } $form->group->setValue($group_ticks); //

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• Advice on software / database design to avoid using cursors when updating database

  - by Remnant

  I have a database that logs when an employee has attended a course and when they are next due to attend the course (courses tend to be annual). As an example, the following employee attended course '1' on 1st Jan 2010 and, as the course is annual, is due to attend next on the 1st Jan 2011. As today is 20th May 2010 the course status reads as 'Complete' i.e. they have done the course and do not need to do it again until next year: EmployeeID CourseID AttendanceDate DueDate Status 123456 1 01/01/2010 01/01/2011 Complete In terms of the DueDate I calculate this in SQL when I update the employee's record e.g. DueDate = AttendanceDate + CourseFrequency (I pull course frequency this from a separate table). In my web based app (asp.net mvc) I pull back this data for all employees and display it in a grid like format for HR managers to review. This allows HR to work out who needs to go on courses. The issue I have is as follows. Taking the example above, suppose today is 2nd Jan 2011. In this case, employee 123456 is now overdue for the course and I would like to set the Status to Incomplete so that the HR manager can see that they need to action this i.e. get employee on the course. I could build a trigger in the database to run overnight to update the Status field for all employees based on the current date. From what I have read I would need to use cursors to loop over each row to amend the status and this is considered bad practice / inefficient or at least something to avoid if you can??? Alternatively, I could compute the Status in my C# code after I have pulled back the data from the database and before I display it on screen. The issue with this is that the Status in the database would not necessarily match what is shown on screen which just feels plain wrong to me. Does anybody have any advice on the best practice approach to such an issue? It helps, if I did use a cursor I doubt I would be looping over more than 1000 records at any given time. Maybe this is such small volume that using cursors is okay?

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• Why aren't min-width and max-width working as I expect?

  - by Nathan Long

  I'm trying to adjust a CSS page layout using min-width and max-width. To simplify the problem, I made this test page. I'm trying it out in the latest versions of Firefox and Chrome with the same results. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Testing min-width and max-width</title> <style type="text/css"> div{float: left; max-width: 400px; min-width: 200px;} div.a{background: orange;} div.b{background: gray;} </style> </head> <body> <div class="a"> (Giant block of filler text here) </div> <div class="b"> (Giant block of filler text here) </div> </body> </html> Here's what I expect to happen: With the browser maximized, the divs sit side by side, each 400px wide: their maximum width Shrink the browser window, and they both shrink to 200px: their minimum width Further shrinking the browser has no effect on them Here's what actually happens, starting at step 2: Shrink the browser window, and as soon as they can't sit side-by-side at their max width, the second div drops below the first Further shrinking the browser makes them get narrower and narrower, as small as I can make the window So here's are my questions: What does max-width mean if the element will sooner hop down in the layout than go lower than its maximum width? What does min-width mean if the element will happily get narrower than that if the browser window keeps shrinking? Is there any way to achieve what I want: have these elements sit side-by-side, happily shrinking until they reach 200px each, and only then adjust the layout so that the second one drops down? And of course... What am I doing wrong?

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• PostgreSQL - fetch the row which has the Max value for a column

  - by Joshua Berry

  I'm dealing with a Postgres table (called "lives") that contains records with columns for time_stamp, usr_id, transaction_id, and lives_remaining. I need a query that will give me the most recent lives_remaining total for each usr_id There are multiple users (distinct usr_id's) time_stamp is not a unique identifier: sometimes user events (one by row in the table) will occur with the same time_stamp. trans_id is unique only for very small time ranges: over time it repeats remaining_lives (for a given user) can both increase and decrease over time example: time_stamp|lives_remaining|usr_id|trans_id ----------------------------------------- 07:00 | 1 | 1 | 1 09:00 | 4 | 2 | 2 10:00 | 2 | 3 | 3 10:00 | 1 | 2 | 4 11:00 | 4 | 1 | 5 11:00 | 3 | 1 | 6 13:00 | 3 | 3 | 1 As I will need to access other columns of the row with the latest data for each given usr_id, I need a query that gives a result like this: time_stamp|lives_remaining|usr_id|trans_id ----------------------------------------- 11:00 | 3 | 1 | 6 10:00 | 1 | 2 | 4 13:00 | 3 | 3 | 1 As mentioned, each usr_id can gain or lose lives, and sometimes these timestamped events occur so close together that they have the same timestamp! Therefore this query won't work: SELECT b.time_stamp,b.lives_remaining,b.usr_id,b.trans_id FROM (SELECT usr_id, max(time_stamp) AS max_timestamp FROM lives GROUP BY usr_id ORDER BY usr_id) a JOIN lives b ON a.max_timestamp = b.time_stamp Instead, I need to use both time_stamp (first) and trans_id (second) to identify the correct row. I also then need to pass that information from the subquery to the main query that will provide the data for the other columns of the appropriate rows. This is the hacked up query that I've gotten to work: SELECT b.time_stamp,b.lives_remaining,b.usr_id,b.trans_id FROM (SELECT usr_id, max(time_stamp || '*' || trans_id) AS max_timestamp_transid FROM lives GROUP BY usr_id ORDER BY usr_id) a JOIN lives b ON a.max_timestamp_transid = b.time_stamp || '*' || b.trans_id ORDER BY b.usr_id Okay, so this works, but I don't like it. It requires a query within a query, a self join, and it seems to me that it could be much simpler by grabbing the row that MAX found to have the largest timestamp and trans_id. The table "lives" has tens of millions of rows to parse, so I'd like this query to be as fast and efficient as possible. I'm new to RDBM and Postgres in particular, so I know that I need to make effective use of the proper indexes. I'm a bit lost on how to optimize. I found a similar discussion here. Can I perform some type of Postgres equivalent to an Oracle analytic function? Any advice on accessing related column information used by an aggregate function (like MAX), creating indexes, and creating better queries would be much appreciated! P.S. You can use the following to create my example case: create TABLE lives (time_stamp timestamp, lives_remaining integer, usr_id integer, trans_id integer); insert into lives values ('2000-01-01 07:00', 1, 1, 1); insert into lives values ('2000-01-01 09:00', 4, 2, 2); insert into lives values ('2000-01-01 10:00', 2, 3, 3); insert into lives values ('2000-01-01 10:00', 1, 2, 4); insert into lives values ('2000-01-01 11:00', 4, 1, 5); insert into lives values ('2000-01-01 11:00', 3, 1, 6); insert into lives values ('2000-01-01 13:00', 3, 3, 1);

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• DirectShow EVR resizing window problem

  - by Daniel

  So I've been looking into the world of media playback for windows and I've started making a C# Media Player using DirectShow. I started off using the VRM-7 windowed video renderer and it was brilliant except it had a couple of small problems (multi monitors, fullscreen). But after some research I found that it's deprecated and I should be using VRM9. So I changed it to use VRM9 windowless then found out that was an old post rofl _< so finally I'm using Vista/Win7 (or XP .net 3) Enhanced Video Renderer (EVR) which is apparently the most up to date Microsoft video renderer and has all the flashy performance/quality things added to it. (tbh I haven't noticed any difference but maybe I need a blue-ray or HQ video to notice it). With using EVR everything is working fine except resizing the video. Its really laggy/choppy/teary and probably something to do with its frame queueing mechanism. To demonstrate my problem open up windows media player classic. View - Options - Playback - output Chose the "EVR" DirectShow Video renderer Now restart wmp class and play a video, while it's playing click and drag a corner to resize it. You'll notice its horribly laggy. This is the exact same problem i am having. But if you chose "EVR Custom Pres. *" or EVR Sync *" resizing works beautifully! So i tried googling around for anything about EVR resizing issues and how to fix it but i couldn't believe how little i could find. I'm guessing "Custom Pres." stands for "Custom Presenter" which sounds like they made their own. Also you'll notice on the right hand size when you swap between EVR and the other EVR's the Resizer drop down on the right greys out. So basically I wan't to know how I can fix this retarded resizing problem and is there any decent documentation out there? There is a fair bit for VMR7/9 but not much for EVR. I downloaded the DirectX SDK which apparently has samples but it was a waste of 500mb of bandwidth as it had nothing relevant. Perhaps there is some way to force it not queueing up frames if that is the problem? If you want code say the word and I'll paste some in. But it's really quite simple and nothing much happens, i'm convinced it's a problem with the EVR renderer. EDIT: Oh and one other thing, what does VLC use? If you go into vlc options and change the renderer to anything but default, they all suck. So is it using VMR7? Or its own?

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• Recommendations for a free GIS library supporting raster images

  - by gspr

  Hi. I'm quite new to the whole field of GIS, and I'm about to make a small program that essentially overlays GPS tracks on a map together with some other annotations. I primarily need to allow scanned (thus raster) maps (although it would be nice to support proper map formats and something like OpenStreetmap in the long run). My first exploratory program uses Qt's graphics view framework and overlays the GPS points by simply projecting them onto the tangent plane to the WGS84 ellipsoid at a calibration point. This gives half-decent accuracy, and actually looks good. But then I started wondering. To get the accuracy I need (i.e. remove the "half" in "half-decent"), I have to correct for the map projection. While the math is not a problem in itself, supporting many map projection feels like needless work. Even though a few projections would probably be enough, I started thinking about just using something like the PROJ.4 library to do my projections. But then, why not take it all the way? Perhaps I might aswell use a full-blown map library such as Mapnik (edit: Quantum GIS also looks very nice), which will probably pay off when I start to want even more fancy annotations or some other symptom of featuritis. So, finally, to the question: What would you do? Would you use a full-blown map library? If so, which one? Again, it's important that it supports using (and zooming in and out with) raster maps and has pretty overlay features. Or would you just keep it simple, and go with Qt's own graphics view framework together with something like PROJ.4 to handle the map projections? I appreciate any feedback! Some technicalities: I'm writing in C++ with a Qt-based GUI, so I'd prefer something that plays relatively nicely with those. Also, the library must be free software (as in FOSS), and at least decently cross-platform (GNU/Linux, Windows and Mac, at least). Edit: OK, it seems I didn't do quite enough research before asking this question. Both Quantum GIS and Mapnik seem very well suited for my purpose. The former especially so since it's based on Qt.

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• Direct show video renderers suck?

  - by Daniel

  So I've been looking into the world of media playback for windows and I've started making a C# Media Player using DirectShow. I started off using the VRM-7 windowed video renderer and it was brilliant except it had a couple of small problems (multi monitors, fullscreen). But after some research I found that it's deprecated and I should be using VRM9. So I changed it to use VRM9 windowless then found out that was an old post rofl _< so finally I'm using Vista/Win7 (or XP .net 3) Enhanced Video Renderer (EVR) which is apparently the most up to date Microsoft video renderer and has all the flashy performance/quality things added to it. (tbh I haven't noticed any difference but maybe I need a blue-ray or HQ video to notice it). With using EVR everything is working fine except resizing the video. Its really laggy/choppy/teary and problem something to do with its frame queueing mechanism. To demonstrate my problem open up windows media player classic. View - Options - Playback - output Chose the "EVR" DirectShow Video renderer Now restart wmp class and play a video, while it's playing click and drag a corner to resize it. You'll notice its horribly laggy. This is the exact same problem i am having. But if you chose "EVR Custom Pres. *" or EVR Sync *" resizing works beautifully! So i tried googling around for anything about EVR resizing issues and how to fix it but i couldn't believe how little i could find. I'm guessing "Custom Pres." stands for "Custom Presenter" which sounds like they made their own. Also you'll notice on the right hand size when you swap between EVR and the other EVR's the Resizer drop down on the right greys out. So basically I wan't to know how I can fix this retarded resizing problem and is there any decent documentation out there? There is a fair bit for VMR7/9 but not much for EVR. I downloaded the DirectX SDK which apparently has samples but it was a waste of 500mb of bandwidth as it had nothing relevant. Perhaps there is some way to force it not queueing up frames if that is the problem? If you want code say the word and I'll paste some in. But it's really quite simple and nothing much happens, i'm convinced it's a problem with the EVR renderer. EDIT: Oh and one other thing, what does VLC use? If you go into vlc options and change the renderer to anything but default, they all suck. So is it using VMR7? Or its own?

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• How to extract the word and line wrapping information from JTextArea for text with given font

  - by Gábor Lipták

  I have to convert styled text to wrapped simple text (for SVG word wrapping). I cannot beleive that the word wrapping information (how many lines are there, where are the line breaks) cannot be extracted from the JTextArea. So I created a small frame program: package bla; import java.awt.BorderLayout; import java.awt.Color; import java.awt.Font; import java.awt.Frame; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.util.ArrayList; import java.util.List; import javax.swing.JTextArea; public class Example1 extends WindowAdapter { private static String content = "01234567890123456789\n" + "0123456 0123456 01234567 01234567"; JTextArea text; public Example1() { Frame f = new Frame("TextArea Example"); f.setLayout(new BorderLayout()); Font font = new Font("Serif", Font.ITALIC, 20); text = new JTextArea(); text.setFont(font); text.setForeground(Color.blue); text.setLineWrap(true); text.setWrapStyleWord(true); f.add(text, BorderLayout.CENTER); text.setText(content); // Listen for the user to click the frame's close box f.addWindowListener(this); f.setSize(100, 511); f.show(); } public static List<String> getLines( JTextArea text ) { //WHAT SHOULD I WRITE HERE return new ArrayList<String>(); } public void windowClosing(WindowEvent evt) { List<String> lines = getLines(text); System.out.println( "Number of lines:" + lines.size()); for (String line : lines) { System.out.println( line ); } System.exit(0); } public static void main(String[] args) { Example1 instance = new Example1(); } } If you run it you will see this: And what I expect as output: Number of lines:6 0123456789 0123456789 0123456 0123456 01234567 01234567 What should I write in place of the comment?

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• dynamiclly schedule a lead sales agent

  - by Josh

  I have a website that I'm trying to migrate from classic asp to asp.net. It had a lead schedule, where each sales agent would be featured for the current day, or part of the day.The next day a new agent would be scheduled. It was driven off a database table that had a row for each day in it. So to figure out if a sales agent would show on a day, it was easy, just find today's date in the table. Problem was it ran out rows, and you had to run a script to update the lead days 6 months at a time. Plus if there was ever any change to the schedule, you had to delete all the rows and re-run the script. So I'm trying to code it where sql server figures that out for me, and no script has to be ran. I have a table like so CREATE TABLE [dbo].[LeadSchedule]( [leadid] [int] IDENTITY(1,1) NOT NULL, [userid] [int] NOT NULL, [sunday] [bit] NOT NULL, [monday] [bit] NOT NULL, [tuesday] [bit] NOT NULL, [wednesday] [bit] NOT NULL, [thursday] [bit] NOT NULL, [friday] [bit] NOT NULL, [saturday] [bit] NOT NULL, [StartDate] [smalldatetime] NULL, [EndDate] [smalldatetime] NULL, [StartTime] [time](0) NULL, [EndTime] [time](0) NULL, [order] [int] NULL, So the user can schedule a sales agent depending on their work schedule. Also if they wanted to they could split certain days, or sales agents by time, So from Midnight to 4 it was one agent, from 4-midnight it was another. So far I've tried using a numbers table, row numbers, goofy date math, and I'm at a loss. Any suggestions on how to handle this purely from sql code? If it helps, the table should always be small, like less than 20 never over 100. update After a few hours all I've managed to come up with is the below. It doesn't handle filling in days not available or times, just rotates through all the sales agents with leadTable as ( select leadid,userid,[order],StartDate, case DATEPART(dw,getdate()) when 1 then sunday when 2 then monday when 3 then tuesday when 4 then wednesday when 5 then thursday when 6 then friday when 7 then saturday end as DayAvailable , ROW_NUMBER() OVER (ORDER BY [order] ASC) AS ROWID from LeadSchedule where GETDATE()>=StartDate and (CONVERT(time(0),GETDATE())>= StartTime or StartTime is null) and (CONVERT(time(0),GETDATE())<= EndTime or EndTime is null) ) select userid, DATEADD(d,(number+ROWID-2)*totalUsers,startdate ) leadday from (select *, (select COUNT(1) from leadTable) totalUsers from leadTable inner join Numbers on 1=1 where DayAvailable =1 ) tb1 order by leadday asc

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• ASP.Net 4.0 - Response required in SiteMap building?

  - by Nick Craver

  I'm running into an issue upgrading a project to .Net 4.0...and having trouble finding any reason for the issue (or at least, the change causing it). Given the freshness of 4.0, not a lot of blogs out there for issues yet, so I'm hoping someone here has an idea. Preface: this is a Web Forms application, coming from 3.5 SP1 to 4.0. In the Application_Start event we're iterating through the SiteMap and constructing routes based off data there (prettifying URLs mostly with some utility added), that part isn't failing though...or at least isn't not getting that far. It seems that calling the SiteMap.RootNode (inside application_start) causes 4.0 to eat it, since the XmlSiteMapProvider.GetNodeFromXmlNode method has been changed, looking in reflector you can see it's hitting HttpResponse.ApplyAppPathModifier here: str2 = HttpContext.Current.Response.ApplyAppPathModifier(str2); HttpResponse wasn't used at all in this method in the 2.0 CLR, so what we had worked fine, in 4.0 though, that method is called as a result of this stack: [HttpException (0x80004005): Response is not available in this context.] System.Web.XmlSiteMapProvider.GetNodeFromXmlNode(XmlNode xmlNode, Queue queue) System.Web.XmlSiteMapProvider.ConvertFromXmlNode(Queue queue) System.Web.XmlSiteMapProvider.BuildSiteMap() System.Web.XmlSiteMapProvider.get_RootNode() System.Web.SiteMap.get_RootNode() Since Response isn't available here in 4.0, we get an error. To reproduce this, you can narrow the test case down to this in global: protected void Application_Start(object sender, EventArgs e) { var s = SiteMap.RootNode; //Kaboom! //or just var r = Context.Response; //or var r = HttpContext.Current.Response; //all result in the same "not available" error } Question: Am I missing something obvious here? Or, is there another event added in 4.0 that's recommended for anything related to SiteMap on startup? For anyone curious/willing to help, I've created a very minimal project (a default VS 2010 ASP.Net 4.0 site, all the bells & whistles removed and only a blank sitemap and the Application_Start code added). It's a small 10kb zip available here: http://www.ncraver.com/Test/SiteMapTest.zip Update: Not a great solution, but the current work-around is to do the work in Application_BeginRequest, like this: private static bool routesRegistered = false; protected void Application_BeginRequest(object sender, EventArgs e) { if (!routesRegistered) { Application.Lock(); if (!routesRegistered) RouteManager.RegisterRoutes(RouteTable.Routes); routesRegistered = true; Application.UnLock(); } } I don't like this particularly, feels like an abuse of the event to bypass the issue. Does anyone have at least a better work-around, since the .Net 4 behavior with SiteMap is not likely to change?

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• Silverlight? WPF? or Windows Form?

  - by Amit

  After Silverlight 4.0 has been released with new WPF, I am kind of confused with these technologies: Silverlight? WPF? Windows Form? The main motive that we want to achieve for BIG business project is following: Performance Security And platform independent** If I consider all above three points then only Silverlight is the option as I don’t want people buying emulator on MacOS for WPF or Windows Form. Now how good the Silverlight is for Business applications, I was completely against when Silverlight 2.0 was in the market but now it is Silverlight 4.0 and they have provided many new features (but still basics) that is required in any challenging business applications. Comparing Silverlight and WPF -* Silverlight and WPF are very new technology and if I'd to compare from these two then I'd prefer WPF because it can be considered stable and mature. But it is not same as Windows Form. -* If I go with Silverlight then I am sure about keep updating to the latest version of Silverlight. I remembered when we were developing software for version 2.0 then we'd to create our own framework with dynamic loading DLL, and then Navigation concept. But everything was got changed once Silverlight 3.0 came. I don't want this to be happening with this new product. -* If we go with WPF then we don't get the platform independence. Now, why not we just focus on making WPF and then move to Silverlght. As someone (Tim?) from Microsoft has said that the idea is to make Silverlight as close as WPF. But if that is the case then why XAML structure is different; I will not be convinced with by saying that .Net framework for SL is too small.. well the difference is coming from the namespace ? I was searching on this subject and found "Microsoft WPF-Silverlight Comparison Whitepaper v1.1.pdf". This guide is very good that gives you ins-outs about how can we build common apps that runs on both. But again, it is comparing Silverlight 2 and not 4. I am sure many architect/ developers/ project managers must be facing similar kind of questions in their premises and wants to initiate this discussion, if it has not been :). We've still got 2 weeks to make this decision, so I'm expecting everyone to participate, gurus?

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• Do Websites need Local Databases Anymore?

  - by viatropos

  If there's a better place to ask this, please let me know. Every time I build a new website/blog/shopping-cart/etc., I keep trying to do the following: Extract out common functionality into reusable code (Rubygems and jQuery plugins mostly) If possible, convert that gem into a small service so I never have to deal with a database for the objects involved (by service, I mean something lean and mean, usually built with the Sinatra Web Framework with a few core models). My assumption is, if I can remove dependencies on local databases, that will make it easier and more scalable in the long run (scalable in terms of reusability and manageability, not necessarily database/performance). I'm not sure if that's a good or bad assumption yet. What do you think? I've made this assumption because of the following reason: Most serious database/model functionality has been built on the internet somewhere. Just to name a few: Social Network API: Facebook Messaging API: Twitter Mailing API: Google Event API: Eventbrite Shopping API: Shopify Comment API: Disqus Form API: Wufoo Image API: Picasa Video API: Youtube ... Each of those things are fairly complicated to build from scratch and to make as optimized, simple, and easy to use as those companies have made them. So if I build an app that shows pictures (picasa) on an Event page (eventbrite), and you can see who joined the event (facebook events), and send them emails (google apps api), and have them fill out monthly surveys (wufoo), and watch a video when they're done (youtube), all integrated into a custom, easy to use website, and I can do that without ever creating a local database, is that a good thing? I ask because there's two things missing from the puzzle that keep forcing me to create that local database: Post API RESTful/Pretty Url API While there's plenty of Blogging systems and APIs for them, there is no one place where you can just write content and have it part of some massive thing. For every app, I have to use code for creating pretty/restful urls, and that saves posts. But it seems like that should be a service! Question is, is that what the website is? ...That place to integrate the worlds services for my specific cause... and, sigh, to store posts that only my site has access to. Will everyone always need "their own blog"? Why not just have a profile and write lots of content on an established platform like StackOverflow or Facebook? ... That way I can write apps entirely without a database and know that I'm doing it right. Note: Of course at some point you'd need a database, if you were doing something unique or new. But for the case where you're just rewiring information or creating things like videos, events, and products, is it really necessary anymore??

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• Dynamic data-entry value store

  - by simendsjo

  I'm creating a data-entry application where users are allowed to create the entry schema. My first version of this just created a single table per entry schema with each entry spanning a single or multiple columns (for complex types) with the appropriate data type. This allowed for "fast" querying (on small datasets as I didn't index all columns) and simple synchronization where the data-entry was distributed on several databases. I'm not quite happy with this solution though; the only positive thing is the simplicity... I can only store a fixed number of columns. I need to create indexes on all columns. I need to recreate the table on schema changes. Some of my key design criterias are: Very fast querying (Using a simple domain specific query language) Writes doesn't have to be fast Many concurrent users Schemas will change often Schemas might contain many thousand columns The data-entries might be distributed and needs syncronization. Preferable MySQL and SQLite - Databases like DB2 and Oracle is out of the question. Using .Net/Mono I've been thinking of a couple of possible designs, but none of them seems like a good choice. Solution 1: Union like table containing a Type column and one nullable column per type. This avoids joins, but will definitly use a lot of space. Solution 2: Key/value store. All values are stored as string and converted when needed. Also use a lot of space, and of course, I hate having to convert everything to string. Solution 3: Use an xml database or store values as xml. Without any experience I would think this is quite slow (at least for the relational model unless there is some very good xpath support). I also would like to avoid an xml database as other parts of the application fits better as a relational model, and being able to join the data is helpful. I cannot help to think that someone has solved (some of) this already, but I'm unable to find anything. Not quite sure what to search for either... I know market research is doing something like this for their questionnaires, but there are few open source implementations, and the ones I've found doesn't quite fit the bill. PSPP has much of the logic I'm thinking of; primitive column types, many columns, many rows, fast querying and merging. Too bad it doesn't work against a database.. And of course... I don't need 99% of the provided functionality, but a lot of stuff not included. I'm not sure this is the right place to ask such a design related question, but I hope someone here has some tips, know of any existing work, or can point me to a better place to ask such a question. Thanks in advance!

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